Research On The Distribution And Possible Source Of OCPs In Agricultural Soil Of Karst Area In Southwest China

Qingmuguan karst valley in Chongqing is selected as the study area in this research, and the agricultural soil as the research object,in order to study the residue characteristic of OCPs under different landuse,discuss the pollution level,the source,the distribution,change rule,migration characteristics;Evaluate the potential ecological risk of OCPs. So as to provide the indispensable scientific theoretical basis and reference for the government and the related environmental protection departments to control soil pollution,better predict the development trend and protect human health and safety,which has the important practical significance.The results show that:(1) The total OCPs concentration in soils of Qingmuguan ranged from 7.29 to 222.42 ng/g with an average value of 46.15 ng/g. HCHs and DDTs existed in all samples.The concentration of HCHs ranged from 0.55 to 26.54 ng/g, and the concentration of DDTs ranged from 4.31 to 213.50 ng/g. DDTs accounts for about 90% of the total OCPs, which is the predominant contamination in the study area. HCHs in study aera came from industrial HCHs and lindane,and under the impact of environment,the compositions of HCH isomers changed significantly. There were still fresh input of DDTs to soils in Qingmuguan underground river catchment,which substantially came from industrial DDTs illegal use, and not the dicofol type of DDT.(2)The total OCPs of three soil profile are 3.36-33.19 ng/g,1.4744.44 ng/g,and 5.9759.14 ng/g. The content of HCHs in three soil profile in this order:the down stream＞the up stream＞the middle stream;The content of DDTs in three soil profile in this order:the down stream＞the middle stream＞the up stream. The content of OCPs reduce with the sampling depth gradually. (3)Through the environment quality assessment and ecological risk assessment indicate that:DDTs has higher ecological risks.Compared to the similar researches in other areas in China,the concentrations of HCHs in soils of Qingmuguan were lower than that of Tianjin, Hangzhou, Shanghai, Guangzhou, Chengdu, equal to Beijing; the concentrations of DDTs in soils of Qingmuguan were lower than that of Tianjin, Beijing, Guangzhou, Chengdu, higher than that of Hangzhou and Shanghai. Compared with researches of foreign countries,the concentrations of HCHs and DDTs in soils of Qingmuguan were higher than that of Germany,Egypt,Romania. Through the potential ecological risks evaluation of OCPs in this research area,we find HCHs has low potential risk on soil invertebrates. Due to the thinner topsoil in karst area,OCPs may through the crack or doline into the underground river system,which is the main of drinking water of local residents. This has the potential threat for ecological environment and human health,and should be taken more attention to.